Nitrocellulose double-base propellant containing butanetrioltrinitrate

ABSTRACT

A nitrocellulose base propellant which contains butanetriol trinitrate in combination with trimethylolethane trinitrate and triethyleneglycol dinitrate. This composition possesses a force potential of at least 380,000 foot-pounds per pound of propellant and an isochoric flame flame temperature below about 3,350*K.

United States Patent 1 Zucker et al.

[4 1 Feb. 18,1975

[ NITROCELLULOSE DOUBLE-BASE PROPELLANT CONTAINING BUTANETRlOLTRINlTRATE [75] Inventors: Jonas Zucker, West Orange; Russell L. Trask, Morris Plains, both of N.J.; Edward Costa, Brooklyn, NY.

[73] Assignee: The United States of America as represented by the Secretary of the Army, Washington, DC.

221 Filed: Mar.26, 1968 21 Appl. No.: 717,487

52 US. Cl. ..149 100,1 49/9 49/ 9 [51] Int. Cl.} ..C06b 5/00 58 Field of Search 149/96, 100, 94

[56] References Cited UNITED STATES PATENTS 3,092,525 6/1963 Cook l49/l00 X Primary Examiner-Stephen J. Lechert, Jr. Attorney, Agent, or FirmEdward J. Kelly; Herbert Ber]; Edward F. Costigan [57] ABSTRACT 4 Claims, N0 Drawings NITROCELLULOSE DOUBLE-BASE PROPELLANT CONTAINING BUTANETRIOLTRINITRATE The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates to a propellant for use in an armor piercing ammunition. More particularly this invention relates to a propellant composition having high force which may be utilized in ammunitions designed for the specialized high pressure artillery pieces in use today.

In the past, the standard mortar propellant compositions, which were of the double-base variety containing about 40 to 50 percent nitroglycerin, possessed isochoric flame temperatures of 3,695K to 3,795K. As a result, a sustained rate of fire for an indefinite period was prohibited because it was found that the barrel of the firing piece in question became overheated and eroded at such a rapid rate during such interval that it would be rendered useless in a relatively short period of time.

As an alternative, it was suggested to utilize propellant compositions of the double-base variety having a nitroglycerin content of only 25 to 30 percent because such compositions possessed isochoric flame tempera tures of 3,080K to 3,130K and a force of 356,000 to 362,000 foot-pounds per pound of propellant. A significant reduction in mortar tube temperature was accomplished upon sustained fire in 81mm mortar when such propellant was utilized in lieu of the the standard mortar composition. For instance, it was found that 142 rounds containing such propellant could be fired at a sustained rate before 1,000F was reached in the mortar tube as compared with approximately 90 rounds for the standard mortar composition. However, this propellant was not acceptable as an alternative because of non-reproducible ballistics resulting from poor velocity and pressure uniformities which were consistently encountered at 40F and occasionally at 70F.

The newly designed high pressure artillery pieces in use today require the use of a propellant having a comparatively high amount of force for use in piercing armor. Another restriction on the propellant, which is to be used in such equipment, is the requirement that it have a low isochoric flame temperature in order to restrict barrel erosion which proceeds at a comparatively fast rate at elevated flame temperatures.

The subject invention answers the needs of the art by providing a force of over 380,000 foot-pounds per pound, which is the equivalent to the force of the standard mortar propellant, at the significantly lower temperatures of alternate propellants suggested for use today. Further, the use of the compositions of this invention is not accompanied by the difficulties and disadvantages which normally are associated with the propellants of the art.

It is therefore an object of this invention to provide a novel propellant composition for use in the specialized high pressure artillery pieces in use today.

Another object is to provide a propellant composition having a force capability of at least 380,000 footpounds per pound of propellant and an isochoric flame temperature below about 3,350K.

A further object is to provide an improved homogeneous propellant composition containing nitrocellulose accompanied by trimethylolethane trinitrate and triethyleneglycol dinitrate into which is incorporated butanetrioltrinitrate.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description.

The concept of this invention is based on the incorporation of butanetrioltrinitrate in a nitrocellulose base propellant which already contains trimethylolethanetrinitrate and triethyleneglycoldinitrate. In this specification, butanetrioltrinitrate is also referred to as BTTN, while trimethylolethanetrinitrate is also referred to as TMETN and triethyleneglycoldinitrate is also referred to as TEGDN. ln order to attain a force level of 380,000 or more foot-pounds per pound of propellant and, at the same time, significantly reduce the isochoric flame temperature, there must be a correspondingly significant increase in gas volume of the resulting composition. This is obvious in view of the equation for force in this particular situation.

Force gas volume x gas constant x isochoric flame temperature.

The above described increase in gas volume is accomplished by the formulation of a homogenous propellant composition containing the mixed nitrate esters described in combination with nitrocellulose. The combination of butanetrioltrinitrate and trimethylolethanetrinitrate results in a far superior gas volume to temperature relationship when compared to the double-base propellants containing nitroglycerin. Further, the presence of triethyleneglycoldinitrate imparts the desired low temperature physical properties.

As noted, the concept of this invention involves the incorporation of BTTN into a nitrocellulose base propellant already possessing TMETN and TEGDN. These mixed nitrates tend to produce a propellant having the desired degree of force at the desired degree of temperature with respect to flame. In this combination, BTTN is utilized to improve the force produced by the propellant upon burning, while also functioning as a plasticizer for the nitrocellulose content of the propellant. The TMETN functions in the conventional manner to increase the gas volume of the propellant which also tends toward increasing force, while TEGDN improves the physical properties at low temperature. These esters may be utilized in the following weight percent to produce an acceptable propellant, viz:

TMETN 5 to 25 TEGDN 2.8 to 3. BTTN 19 to 29 If we go above these specific percentages, the normal propellant will be relatively soft resulting in loss of grain integrity which will cause unpredictable variations in burning rate. Below these percentages, the composition will be unsatisfactory for extrusion or rolling purposes as a result of the hardness of the propellant.

The preferred range of BTTN in weight percent when utilized with the specific nitrate esters above described is as follows, viz:

TMETN 5 to 25 TEGDN l to 5 BTTN 22 to 26 weight percentages of the nitrate esters were in the following specific range, viz:

TMETN 14 to 16 TEGDN l to B'ITN 22.4 to 25.6

1t was also found that within the latter ranges, that the composition was reproducible from lot to lot with respect to force and flame temperature.

In general, the propellant composition of this invention may be prepared for use in the manner described below.

EXAMPLE I Nitrocellulose having a nitrogen content of approximately 13.15 percent is added to a conventional sigmablade mixer in an amount between 44.5 and 56.5 perwith respect to force and flame temperature when the r M26E1 and M8 represent propellants within the art' cent by weight of the propellant. A maximum of 1.0 percent of an inorganic salt such as potassium sulfate, potassium aluminum fluoride or sodium aluminum fluoride may be added to the mixer, if it is desired to reduce the flash of the propellant product. If a flash reducer is added, it should be mixed with the nitrocellulose for 5 to 10 minutes prior to the addition of the remaining ingredients. A mixture of 42 to 54 percent by weight of the mixed nitrates described above are then added to the mixer under agitation and mixing is continued from 5 to 10 minutes. At this point, 1.5 percent of a stabilizer such as diethyldiphenylurea (ethyl centralite), which is'wetted with'aleohol, is then added and mixing continued from 5 to 10 minutes. Solvents making up 14 to 27 weight percent of the total composition are then added to the mixture. This liquid component should consist of 38 to 52 parts of acetone and 48 to 62 parts by weight of alcohol. After the solvents are added, mixing should be continued for a maximum of 3 hours at approximately to F. As a result of the above processing, a uniform, extrudable colloid is produced" which may be treated in the conventional manner to form specific grain geometries.

' Compositions prepared in accordance with the above procedure and which fall within the concept of this invention are compared to the conventional propellant compositions in the Table which follows. The compositions designated as Expt 3047, 3249 and 2923 represent various embodiments of this invention, whereas which are use today.

TABLE I Expt Expt Expt Propellant M26E1 M8 3047 3249 2923 Composition Nitrocellulose, percent by weight 68.70 52.15 56.50 53.70 44.50

(Percent Nitrogen in Nitrocellulose) (13.15) (13.25) (13.15) 13.15) (13.15) Nitroglycerin, percent by weight 25.00 43.00 Butanetrioltrinitrate do. 24.00 25.60 24.00 Trimethylolethanetrinitrate do. 15.00 16.00 25.00 Triethyleneglycoldinitrate do. 3.00 3.20 5.00 Potassium nitrate do. 1.25 Diethylphthalate do. 3.00 Diethyldiphenylurea do. 6.00 0.60 1.50 1.50 1.50 Graphite do. 0.30 Graphite (glaze) do. 0.10 0.10 0.10 0.10 Residual water do. 0.20 0.00 0.40 0.50 0.50 Residual ethyl alcohol do. 0.70 0.40 0.40 0.50 0.50

Expt Expt Expt Propellant M26E1 M8 3047 3249 2923 Thermochemical Characteristics lsochoric Flame Temperature, K 3130 3695 3320 3333 3331 Force. ft-lbs/lb 362,000 382,000 380,300 382,400 388,600 Heat of Explosion, cal/gm 977 1244 1072 1081 1081 Unoxidized Carbon, percent 1.5 Zero Zero Zero 0.9 Combustibles (CO+H percent 56.3 37.2 50.5 50.2 50.8 Gal Volume, moles/gram 0.04164 0.0371 1 0.04116 0.04124 0.04187 Propellant Y M26E1 M8 Mechanical Properties Temperature, F 70 40 160 70 -40 Maximum Stress, psi 4390 12637 22,068 609 4364 14,053 Compression at Max Load, 62.4 55.9 8.3 68.8 58.1 40.6

Expt 3047 Expt 3249 Expt 2923 Temperature, F' 160 70 -40 160 70 -40 160 70 -40 Maximum Stress, psi 4595 9988 20,306 2262 5079 15.228 3669 2405 "15,228 Compression at Max Load, 73.2 60.3

It is to be noted that the isochoric flame temperatures for the compositions within this invention are approximately 370K cooler than that for the conventional M8 propellant, whereas their force values are comparable or superior. An examination of Table I shows that the Expt 2923 formulation, which has an isochoric flame temperature of 3,33 1K, is 464K cooler than the standard mortar propellant with an accompanying increase in force of approximately 6.600 foot-pounds of propellant. The presence of the mixed nitrate esters in composition Expt 3047 results in an increase in force of about 18.000 foot-pounds per pound of propellant over that of the standard M26El propellant. Yet, this is accompanied by less than a 200K increase in isochoric flame temperature. Further, all three compositions falling within the present concept have compression values at low temperature either comparable or superior to the standard M8 propellant and vastly superior to the cooler M26El composition.

It has been found that compositions falling within the concept of this invention have superior physical strength under arctic conditions and'are not susceptible to fracture of the grain as pressure builds upon burning. Thus, gun destruction based on the above is totally avoided. Further, the relatively low isochoric temperatures of the propellants of this invention insure that there will be less erosion of the artillery piece in which the propellant is used. Also, the force produced by the prescnt propellants have been found to give the ultimate velocity possible within the set pressure limits of today's specilized high pressure artillery pieces.

Obviously, there are many modifications and variations of the present invention which are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

We claim:

1. In a double based propellant containing nitrocellullOSe and the mixed nitrate esters of trimethylolethanel trinitrate and triethylene glycol dinitrate, the improve ment consisting of the incorporation therein of butanetrioltrinitrate to achieve a propellant having a force of at least 380,000 foot pounds per pound of propellant and an isochoric flame temperature below about 3 ,350K.

2. The propellant of claim 1 wherein said butanetrioltrinitrate is present in an amount between about 19 and 29 percent by weight based on the weight of said propellant.

3. The propellant of claim 1 wherein said butanetrioltrinitrate is present in an amount between about 22 and 26 percent by weight based on the weight of said propellant.

weight of said triethyleneglycoldinitrate.

=l l l 

1. IN A DOUBLE BASED PROPELLANT CONTAINING NITROCELLULOSE AND THE MIXED NITRATE ESTERS OF TRIMETHYLOLETHANETRINITRATE AND TRIETHYLENE GLYCOL DINITRATE, THE IIMPROVEMENT CONSISTING OF THE INCORPORATION THEREIN OF BUTANETRIOLTRINITRATE TO ACHIEVE A PROPELLANT HAVING A FORCE OF AT LEAST 380,000 FOOT POUNDS PER POUND OF PROPELLANT AND AN ISOCHORIC FLAME TEMPERATURE BELOW ABOUT 3,350*K.
 2. The propellant of claim 1 wherein said butanetrioltrinitrate is present in an amount between about 19 and 29 percent by weight based on the weight of said propellant.
 3. The propellant of claim 1 wherein said butanetrioltrinitrate is present in an amount between about 22 and 26 percent by weight based on the weight of said propellant.
 4. The propellant of claim 1 wherein said butanetrioltrinitrate is present in the amount of between about 22.4 and 25.6 percent by weight based on the weight of said propellant, and said trimethylolethanetrinitrate is present in the ratio of 5 parts by weight to 1 part by weight of said triethyleneglycoldinitrate. 